Blocking is a poor remedy for personality conflicts on forums and most sites don't do it. Facebook is actually kind of unique in the social media I've been involved with in that it will actually completely hide two individuals from each other. Everywhere else, reasonable community guidelines, effective moderation and community policing generally do the job well.
One of the video game sub-forums here at GS was essentially taken over by one bad actor who went from site to site to harass specific individuals. On other sites (such as Grogheads and the Matrix forums), she (or he) was called out by the administrators and never gained much traction. Here, they enjoyed the more liberal free speech culture of GS. The specific sub-forum they took over died out, by a combination of lessening interest in the game itself and their own abusive behavior driving others away. Disappointing but the community for that specific video game was probably not that strong anyway. Even if the moderators had decided to act in opposition to the free speech culture enjoyed here, and banned that alleged bad actor outright, it wouldn't have salvaged much as the game was an older title and interest had declined to the point few really wanted to post on topic there anymore.
From what I've seen, the viable sub-forums here have communities that don't stand for true instances of harassment and are able to self-police. Supporting free speech (even within reasonable limits) often means standing up for others to say things you don't like or agree with. This site perhaps more than others has favoured freedom of expression over individuals claiming to be offended and has been moderated pretty consistently in that regard. It's a public forum, after all.
Having said that, I've agreed with Cary's calls for civility and his belief we can all do better. I get the feeling people are genuinely taking it to heart.